Transmitter



March 23, 1943. FECKER 2,314,487

TRANSMITTER Filed Feb. 12, 1941 2 Sheets-Sheet 1 22 m m mo ZSnnentor THEOUOR EEC/(ER;

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attorney March 23, 1943. T, FECKER' 2,314,487

TRANSMITTER 4 Filed Feb. 12, 1941 2 Sheets-Sheet 2 (Ittomeg Patented Mar. 23,1943 V UNITE STATES. PATE T OFFICE TR AN SMITTER Theodor Fecker, Berlin, Germany, asslgnor to g General Electric Company, acorporation of New York 7 Application February 12, 1941, Serial No. 378,523

r I In GermanyFebruai-y 4, 1939 4Cl ainis. (Cl.179171l I This invention is concerned with a circuit organization-designed to improve the efilciency of medium frequency or high-frequency tube transmitters, more particularly, push-pull tube transmitters. The innovation is that a choke coil is included between the direct current source of supply and the oscillation cir-. cuit representing the load, and that control acimpulse-controlled In arrangements of this nature. therefore,'the aim .is as stable as possible a current strength throughout the duration of the impulse and thus also for each individual alternation of the keyed frequency. At first sight this would appear impossible for, as will be seen from the diagram Fig.- 1.which applies toa conventional valve tion is'hrought upon the transmitter tubes by a preferablyrectangulargrid control potential in sucha way that the alternations of plate cu-r-.

rent are more or less rectangular and that they v preferably have a stable current strength roughly corresponding to the current carrying capacity of the'tube. Theinvention is of value in transmitterslbecause, as is well known; a squarevwave delivers more energy than any other shape wave of the same duration and peak value. Thus, if peak value of plate pulse is not to exceed certain allowable tube rating,.and duration is to be small so as to get-high efficiency, then maximum power will beldeliveredby a squarishpulse. My invenoperate when modified in accordance with my invention; and

Figs. 4and 6 illustrate two modifications of wave generatingsystems arranged in accordance with my invention.

In valve or tube transmitters 'working with electron tubes, especlally-push-pull power tube arrangements, theefficiency as well known is governed to a considerable degree by the dissipation of the electron tubes themselves. A reduction of the dissipation becomes particularly important in caseswhere the load capacity of tubes is to be pushed to the uttermost limit.v A case of this kind arises in connection with the generation of brief transmitter impulses of the highestpossible power. impulses modulated by medium or high frequency may be pushed to an extreme point a' very high tube load is permissible because of the cornparatively great impulsedur'ation, the produced power naturally being a function of the utilization thereof throughout the length of the im- 1 pulse.

In order that the impulse energy of the I transmitter circuit organization of a kind shown in Fig. 2,-in the presence of rectangular plate --current ial the dissipation Va of the tubes ID for a semi-cycle would have a very uneconomical shape insofar as at the beginning and towards the end of the semi-cycle it would be required torhave far higher values than in the intermediate value or crest. This shape follows from the time change of the tube potential between anodes l4 and cathodes l6 which consists of the difference between the direct current voltage U: of

thesource of direct current potential supply and the alternating potential U which adjusts itself at the oscillatory circuit 20 forming the load in the plate circuit of the valve arrangement.

The aggregate loss or dissipation conditioned thereby is very liable to assume large proportions so that the efficiency drops far below the 50 percent level.

Another cause for loss in based upon thefact that the time interval of a rectangular current in eachsemi-cycle of transmitted frequency is restricted to a comparatively narrow; range in the'neighborhoodof the crestvalue of the voltage curve. In this case, of course, the dissipation of the tube will not reach high instantaneous values. But operation or this kind inheres the drawback thatthe current during such abbreviated period of current flow would have to have a correspondingly higher amplitude if the same total power is to be obtained. Equal power at the same tubedssipa tion would thus have to be *securedwithhigher tube load, in other words, by the use of larger and morepowerful transmitter valves.

On the other hand, it is also conceivable that by sine-wave control. of the tubes the. plate cur-Q rent ml is lowered towards the beginnings and ends of the semi-cycles as compared with its maximum instantaneous values. Such kindof control action would be readily possible also by application to the grids 22 of a suitably dimen-.

sioned sinusoidal grid alternating potential-ugi optionally in combination with a blocking grid direct current potential ug=.

gram (Fig. 3) this, to be sure, results in a tube dissipation Va-which is a function of the time, and is improved as compared with the tube disefiic'iency may be I As shown in dia-, v

- applied by the winding mitter equipment as'to the sipation Vd shown in Fig. 1. In this case there is the drawback that the current-carrying capacity of the tubes pushed to a particularly high level under certain circumstances cannot be fully utilized for the production of useful or signal power for the reason that the plate current must always be lowered under the value corresponding to the load-.carrying'capacity of the tube. I

Now, the aim-and purpose of the invention is to combine satisfactory utilization of the tube with the lowest possible dissipation and to thereby assure, with a given tube, actually the highest possible useful energy in the presence or the lowest possible input energy; or inversely, ior a given useful power, to get along with the lowest possible dimensions for transmitter tubes, weights or the circuit elements.

=rd r1g to the invention this problem is solved, as illustrated in Fig. 4, by inserting a butier choke 30 in the plate circuit 20 of the circuit organization or the transmitter between the diof becomes practically a direct current which is invariable throughout the whole impulse length.

Such control action is obtainable by using rectangular grid voltage curves or else by a. grid alternating potential at least resembling this form. However, there are also other ways and means adapted thereto, vfor instance, current ieedbackby means of coupling inductances 50 and 52 in the plate and grid circuits respectively with the plate circuits carrying rectangular semicurrents as indicated in purely schematic form in Fig. 6. In this modification the action of the choke 30 as described above is supplemented by the energy source and that is, the lowest cost and r the feed-back action of windings 50 and 52. The

choke 30 again squares up the pulses at the outputs so that they are more nearly of square wave form rather than peaked as shown at ial of Fig. 3; The feed-back at 50 and 52 boosts the excitation voltage on the grids 22 and 24 to further reot current voltage source of supply 33 furnishingthe plate energy and the oscillatory circuit which delivers the produced alternating cur-- rent energy. The said choke coil according to the sense and'purpose of the invention takes up the voltage differences between the direct current potential supplied alternating potential of the oscillatory circuit 20 with the result that the potential at the trans-.-

mitter valves is practically stabilized; that is, roughly potential (Fig. 1). In connection therewith the invention provides for the full swirg or drive of plate current at constant amplitude throughout each, semi-cycle, for instance, by the aid of .arectangular grid control alternating potential 40. Since thus both the plate current as well as the plate potential may simultaneously be of rectangular form,

the dissifrom source 33 andthe square up the excitation voltages on the grid, which, as stated hereinbeiore, may be of sinewave, or, better yet, of squareewave' .form, such as, high frequency pulses such as obtained-by: keying a high frequency generator coupled to the input winding 01 40. It will be noted that the invention, offers very great advantages above all in connection with the operation of impulse transmitters for the rea-- son that it insures an increase in eiil'ciency without an incidental impairment in the extreme uti lization of the highload-carrying capacity of the in accordance with the value of the tube v pation which thus results will be comparatively low and practically constant throughout the semi cycle. In other words, the efllciency will reach the highest possible value. But, also, the overall efiiciency of the whole transmitter arrangement is raised in direct proportion to the tube utilization; in other words, with the same crest current impulse duration, bya

values, within the same circuit organization according tothe invention,

larger powers can be handled and be delivered by.

tubes inside brief periods of time. In the last 1 analysis theinvention, therefore, is adapted .to; the-productiono! extremely high impulsepowers by means or. small direct current energies and transmitter valves utilized to the fullest. limit; 5 By using the basic idea 01 the invention increases oi efliciency of 100 and more percent are possible compared with theperformance obtainable without. the invention. i

1What is claimed is: 1.- In a radio frequency ixphase opposition on said control grids, an oscilthe oscillator than=has been feasible with circuit;

organizations previously described. The situation and conditions resulting in a circuit arrangement of the invention as to the rest are illus trated by the graphs of- Fig. 5' especially voltage- Udr arising in choke coil 30. These graphs will be readily 'understandable in the light of what has been stated by reference to- Figs. 1, 2 and 3.

The increase in efilciency which, under certhat of the effective dissipation ocplate dissipation, a.-

latory-circuit connected with said anodes, and means for supplying substantially constantjdirect current to the anodes of said tubes. E.

2. In an amplifier system, a pairof electron discharge tubes each having an anode, a cathode,

and a control grid, means for impressing wave energy of square wave form inpush-pull relation.

on-said "control. grids, an oscillatory circuit including an inductance connecting said anodes in .push-pullrelation, a direct current source havto tain circumstances may be very appreciable bying a negative terminal connected to the cathodes of said tubes, and a choke coil connecting a positive. terminal, of said source to a point on the inductance of said oscillatory circuit-Ior-supplying substantially constant directcurrentto the anodes of saidtubes;

3. In a radio frequencyamplifier. system, a pair of electron discharge tubes each having an anode;

a cathode, and a control grid, a'radio frequency circuitconnectingthe control grids of:said tubes ln'push-pull relation, connections for impressing wave energy or square wave form'in phase opposition on said controlgrids, an alternating current, circuit including an; inductance connected between the anodes of; said tubes, -means for Because of the control action .plate currents alternate; abruptly with the result that the sum total there-' maintaining allpOints' onsaid alternating current circuitat radio frequencypotential and for supplying substantially constant direct, ,current to .the anodes of said tubes, including aradio freamplifier system, a pair of electron discharge tubes each having; an anode, arcathode, and acontrol grid; means for impressing wave energy of square wave form'in quency choke coil and a source 01' potential connected in series between a point on said inductance and the cathodes of said tubes.

4. In an amplifier system, a pair of electron discharge tubes each having an anode, a cathode, and a control grid, means for impressing wave energy of substantially square wave form in push-pull relation onsaid control grids, an alternating current circuit including reactances tuned to the frequencyiof the said wave energy 10 connected between the anodes of said tubes, connections including an inductance of high impedance to wave energy of the frequency of said impressed wave energy for connecting a source of direct current between the anodes and oathodes of said tubes, said connections and inductance serving to supply substantially constant direct current to the anodes of said tubes, and a regenerative coupling between the anode and the control grid of each of said tubes.

THEODOR FECKER. 

